Obtaining Nernstian response of a Ca(2+)-selective electrode in a broad concentration range by tuned galvanostatic polarization.

Linear Nernstian response is obtained for a neutral ionophore-based Ca(2+)-selective electrode down to 10(-10) M CaCl2 by means of galvanostatic polarization. The densities of the applied cathodic current were tuned for particular concentrations of Ca2+. The procedure included recording the potential at zero current, followed by measurements when current is passed through the electrode, and then again at zero current.

Potentiometric estimation of the stability constants of ion-lonophore complexes in ion-selective membranes by the sandwich membrane method: theory, advantages, and limitations.

Segmented sandwich membrane method of studying stoichiometry and stability constants of ion-ionophore complexes in ion-selective membranes is considered in detail. The experimental data (reported earlier in Russian) concerning complexes of various ions with valinomycin, with H+-selective neutral ionophore hexabutyltriamidophosphate, and with anion-binding neutral ionophore p-hexyl trifluoroacetylbenzoate is presented in a compact form. Advantages of titration technique in the sandwich membrane method (the presence of an internal criterion of reliability, and the possibility of direct determination of complex stoichiometry coefficients) are specially addressed.